Terpenes are widespread in nature, mainly in plants as constituents of essential oils. Many terpenes are hydrocarbons, but oxygen-containing compounds such as alcohols, aldehydes or ketones (terpenoids) are also found. Their building block is the hydrocarbon isoprene, CH2═C(CH3)—CH═CH2 (isoprene rule, Wallach 1887). Terpene hydrocarbons therefore have molecular formulas (C5H8)n, they are classified according to the number of isoprene units:
number of isoprene unitsmonoterpenes2sesquiterpenes3diterpenes4triterpenes6tetraterpenes8
Examples of monoterpenes are: pinene, nerol, citral, camphor, geraniol, limonene. Examples of sesquiterpenes are: nerolidol, farnesol. Examples of diterpenes are: vitamin A1 (retinol). Squalene is an example of a triterpene, and carotene (provitamin A1) is a tetraterpene.
The term “terpenoid”, for purposes of the present invention, is intended to cover terpenes and derivatives thereof having at least one C5H8 hydrocarbon unit with one or more points of unsaturation within the chemical structure.
Terpenoids are useful organic compounds in many industries, particularly in resins, perfumes, fragrances, etc. Terpenoids are a fragrance raw material of many perfumes and scents. Fragrance terpenoids are disclosed in Arctander, S., Perfume and Flavor Chemicals, Vol. I and II, Allured Pub. Co. (1969) and examples include Ambregris odor chemicals, Jasmones, Musks, Pyran-derivatives, and Sandalwood fragrance chemicals.
It is well known that mixtures of perfume or fragrance raw materials when deposited on a surface or when incorporated in a cosmetic composition lose intensity and may change character with time, due to many factors. Many attempts have been made to minimize these drawbacks, but so far with minimal success. For example, Gardlick et al, U.S. Pat. No. 6,147,037 relates to fragrance delivery systems useful in delivering sustained or enduring fragrances to personal care items.
One factor responsible for loss of fragrance intensity or change in character is that terpenes are oxidatively unstable. The degree of oxidative instability depends on the degree of unsaturation, or the number of double or triple bonds in the organic compound.
Oxidative instability is an undesirable characteristic in terpenoids. There is a need, therefore, for an agent that will stabilize terpenoids against oxidation. In particular, there is a need for an agent that will prevent the oxidation of terpenoids which have at least one double bond in its chemical structure.